Disk drives are information storage devices that use magnetic media to store data and a movable read/write head positioned over the magnetic media to selectively read data from and write data to the magnetic media.
Consumers are constantly desiring greater storage capacity for such disk drive devices, as well as faster and more accurate reading and writing operations. Thus, disk drive manufacturers have continued to develop higher capacity disk drives by, for example, increasing the recording and reproducing density of the information tracks on the disks by using a narrower track width and/or a narrower track pitch. However, each increase in track density requires that the disk drive device have a corresponding increase in the positional control of the read/write head in order to enable quick and accurate reading and writing operations using the higher density disks. As track density increases, it becomes more and more difficult to quickly and accurately position the read/write head over the desired information tracks on the disk. Thus, disk drive manufacturers are constantly seeking ways to improve the positional control of the read/write head in order to take advantage of the continual increases in track density.
One approach that has been effectively used by disk drive manufacturers to improve the positional control of read/write heads for higher density disks is to employ a voice coil motor (VCM). Referring to FIG. 1a, a conventional disk drive device using VCM typically has a drive arm 104, a HGA 106 attached to and mounted on the drive arm 104, a stack of magnetic disks 101 and a spindle motor 102 for spinning the disks 101. The employed VCM is for controlling the motion of the drive arm 104 and, in turn, controlling a slider 103 of the HGA 106 to position with reference to data tracks across the surface of the magnetic disk 101, thereby enabling the read/write head imbedded in the slider 103 to read data from or write data to the disk 101. However, because the inherent tolerances of the VCM 105 and the HGA 106 exist in the displacement of the slider 103 by employing VCM 105 alone, the slider 103 cannot achieve quick and fine position control which adversely impacts the ability of the read/write head to accurately read data from and write data to the disk 101.
In order to solve the problem, an additional actuator, for example a PZT (piezoelectric) micro-actuator, is introduced in the disk drive device in order to modify the displacement of the slider 103. The PZT micro-actuator corrects the displacement of the slider 103 on a much smaller scale, as compared to the VCM, in order to compensate for the resonance tolerance of the VCM and/or the HGA. The micro-actuator 105 enables, for example, the use of a smaller recording track pitch, and can increase the “tracks-per-inch” (TPI) value by 50% for the disk drive unit, as well as provide an advantageous reduction in the head seeking and settling time. Thus, the PZT micro-actuator enables the disk drive device to have a significant increase in the surface recording density of the information storage disks used therein.
Referring to FIGS. 1a and 1b, the PZT micro-actuator has two piezoelectric elements 107. The piezoelectric elements 107 are mounted within the HGA 106. The HGA 106 includes a suspension 110 to support the slider 103 and the piezoelectric elements 107. The suspension 110 comprises a flexure 111, a slider support 112 with a bump 112a formed thereon, a metal base 113 and a load beam 114 with a dimple 114a formed thereon. The slider 103 is partially mounted on the slider support 112 with the bump 112a supporting the center of the back surface of the slider 103. Specifically, the flexure 111 provides a plurality of traces thereon. The traces of the flexure 111 couple the slider support 112 and the metal base 113. Referring to FIG. 1c, the flexure 111 forms a slider mounting region 111a for positioning the slider 103 and a tongue region 111a for positioning the two piezoelectric elements 107 of the micro-actuator. FIG. 1d shows that the slider 103 and the two piezoelectric elements 107 are mounted on the flexure 111. Specifically, the slider 103 is mounted on the slider mounting region 111a of the flexure 111, and the piezoelectric elements 107 are mechanically mounted on the tongue region 111b of the flexure 111 via epoxy. The piezoelectric elements 107 forms pads 101b, 102b and 103b, wherein pad 101b, 103b are respectively formed on the left, right element of the piezoelectric elements 107 and the pad 102b is a common pad of the two piezoelectric elements 107. The suspension 110 forms pads 101a, 102a, 103a at positions thereof corresponding to pads 101b, 102b and 103b of the piezoelectric elements 107, wherein the pad 102 of the suspension 110 is grounded. The piezoelectric elements 107 are electrically connected with the suspension 110. Specifically, the pads 101b, 102b, 103b of the piezoelectric elements 107 are respectively and electrically connected with the pads 101a, 102a, 103a of the suspension 110 via metal material such as wires 101, 102, 103. Referring to FIG. 1e, when a voltage is input to the two piezoelectric elements 107 of the PZT micro-actuator, one of the piezoelectric elements may contract as shown by arrow D while the other may expand as shown by arrow E. This will generate a rotation torque that causes the slider support 112 to rotate in the arrowed direction C and, in turn, makes the slider 103 move on the disk. In such case, the dimple 114a of the load beam 114 works with the bump 112a of the slider support 112, that is, the slider 103 together with the slider support 112 rotates against the dimple 114a, which keeps the load force from the load beam 114 evenly applying to the center of the slider 103, thus ensuring the slider 103 a good fly performance, supporting the head with a good flying stability.
However, the piezoelectric elements 107 and the suspension 110 of the prior art are both manufactured separately via individual process and individual factory, and the piezoelectric elements 107 are mechanically and electrically connected to the suspension 110 via assembly procedure. Such manufacturing process is extremely complex, and the head gimbal assembly manufactured has a low manufacture yield, a poor work performance and a long process time. First, as the piezoelectric elements 107 are thin film piezoelectric elements which possess a thickness of about 1˜10 um and are terribly fragile, thus the piezoelectric elements 107 are very easy to deform to result in damage, thereby the piezoelectric element mounting operation is quite difficult. Besides, as mechanically mounting piezoelectric elements 107 to the tongue region 111b of the flexure 111 is accomplished by bonding adhesive, thus the control of adhesive (such as adhesive viscosity, adhesive strength and adhesive thickness, etc) is very difficult, and as the amount of adhesive could affect mechanical performance, dynamic performance and static performance of the head gimbal assembly, such as displacement performance and resonance performance, thus the thickness and volume of the adhesive must be appropriate, which adds more difficulty in controlling adhesive' amount during piezoelectric element mounting process. Moreover, as the connection position of the piezoelectric elements 107 and the suspension 110 is at the tongue region 111b of the flexure 111, and the electrical connection is performed by welding, thus the welding operation is of great difficulty, and accordingly, the head gimbal assembly results in a low manufacture yield, a long time consumption, and a low connection reliability.
Hence, it is desired to provide an improved method for manufacturing a head gimbal assembly and a head gimbal assembly manufactured by the method, and a disk drive unit to solve the above-mentioned problems.